Benji Marshall's manager Martin Tauber has confirmed the NRL superstar will turn his back on the code and play rugby union.

Marshall shocked the Wests Tigers on Monday night by demanding to be released from the final two years of his contract after failing to agree terms on an upgraded deal.

The Auckland-based Blues Super Rugby franchise are believed to be in pole position to sign Marshall and Tauber said the 28-year-old will be gone from the NRL at the conclusion of the 2013 campaign.

Tigers skipper Robbie Farah admitted on Tuesday he was shocked by Marshall's decision, but Tauber said the breakdown in negotiations with the joint-venture is the main reason for his exit.

Marshall is believed to have had a handshake agreement with former CEO Stephen Humphreys for an upgraded and extended contract through to the end of 2017.

But his future became murky when Humphreys stood down two months ago.

"He's given 13 years of his life to the club and he needs a change," Tauber told Fox Sports.

"The protracted negotiations began in January and here we are in July and we still don't have a firm and fixed agreement.

"We've had handshake deals that under the previous CEO that never eventuated before he resigned ... and that hasn't been fulfilled.

"I understand that business is business and the club have still given us what is still a very healthy offer but Benji has made his decision."

Tauber said Marshall, who debuted for the Tigers in 2003 and inspired the joint-venture to their first ever premiership two years later, wouldn't entertain the prospect of joining another NRL team and is ready to play rugby.

He also revealed his client has consulted Israel Folau about playing the 15-man game before making his decision known to the Tigers.

"The figures are not important he just feels he needs to get his mojo back and feels he's going to have to do that in rugby," Tauber said.

"He made a vow to never play for another club. He is too loyal to that club to do that to the fans or the sponsors who have supported him for the last 12 years."

Tauber also accused the NRL of doing nothing to keep Marshall in the game and was surprised at a lack of contact from the game's hierarchy.

"You would think that for someone that brings the quality to the game, the merchandising, kids enjoyment for rugby league that someone would have picked the phone up and said 'is there anything we can do to help?', Tauber said.

"But we've heard nothing.

"He's already had a conversation with Izzy about playing rugby - they'd be a devastating duo."

Tigers acting CEO Grant Mayer said he was taken aback when he was told of Marshall's decision on Monday evening and a release is unlikely to be granted until it's ratified by the board later this week.

"We were very, very confident that we were headed in the right direction with Benji but the phone call last night was surprising," said Mayer.